Rotating shaft apparatus

Abstract

A shaft 17 defines a front end portion 17a having a larger diameter and an opposite tail end portion 17b having a smaller diameter, the shaft 17 being rotatably supported by the housing 13 through a radial bearing 19 and a pair of angular ball bearings 21 at the front side large diameter portion 17a and the small diameter portion 17b, respectively.

Description

TECHNICAL FIELD[0001]The invention relates to a rotating shaft apparatus such as a spindle apparatus of a machine tool or an industrial machine.BACKGROUND ART[0002]The shaft of a rotating shaft apparatus, such as a spindle of a machine tool, receives radial and thrust load. Therefore, the bearings rotationally supporting the shaft are determined in consideration of such loads. For example, Japanese Patent No. 3080253, as a first prior art, discloses a spindle which is rotatably supported by a pair of angular ball bearings and a radial ball bearing, at the front and tail end portions of the spindle, respectively. In general, a pair of angular ball bearings are disposed at the front side of the spindle. Further, Japanese Unexamined Patent Publication (Kokai) No. 7-310742, as a second prior art, discloses a configuration of a spindle which is rotatably supported by a pair of angular ball bearings and a cylindrical roller bearing, at the front and tail end portions of the spindle, respe...

AI Technical Summary

Benefits of technology

[0011]The present invention is directed to solve the above-described problems of the prior art and the objective is to provide a rotating shaft apparatus adapted to a high speed and high rigidity of the shaft.

[0012]Further, the objective of the invention is to provide a rotating shaft apparatus adapted to provide a high speed and high rigidity of the shaft by optimizing the cooling of the shaft and the housing.

[0013]Further, the objective of the invention is to provide a rotating shaft apparatus in which the temperatures of the inner and outer races of the bearings supporting the shaft and the coolant are separately controlled on the basis of detection results to control the internal pressure of the bearings disposed between the shaft and the housing, which prevents damage to the bearings.

Problems solved by technology

The higher the DN value of a shaft, the shorter the life of the bearings supporting the shaft becomes and, therefore, expensive bearings are required.

Particularly, in an angular ball bearing, contacting angles are defined between the balls and the inner and outer races, which results in spinning motions of the balls and slippage of balls relative to the inner and outer races, which further results in rupturing the lubricating oil film.

According to the second prior art, although the spindle is rotatably supported at the tail end portion by the back-to-back angular bearings, the spindle is formed with a constant diameter in the longitudinal direction, and therefore there is a problem, the same as in the first prior art, in connection with the increase in DN value accompanied with the increase in the rotational speed and the diameter of the shaft.

In such a case, if the housing is too cool, excessive internal pressure is applied to the rolling elements disposed between the inner and outer races, because the outer race cannot thermally expand.

Therefore, the internal race and the rolling elements are urged to the outer race so that the heat generation due to the friction between the inner race, the outer race and the rolling elements is increased, which results in damage to the bearing.

Therefore, a cooling condition of the housing cannot be clearly obtained and optimal control of the temperatures of the spindle and the housing cannot be conducted.

Therefore, according to the configuration of the third prior art, there is a problem that an optimal control of the temperatures of the inner and outer races of the bearings, attached to the spindle and the housing, respectively, cannot be conducted.

However, according to the fourth prior art, the temperatures of the inner and outer races are not measured and, therefore, the heat generated by the friction between the inner race, the outer race and the rolling elements cannot be eliminated, which may result in seizure of the bearing.

Therefore, the temperature of the heat generating portion in the bearing cannot be precisely detected because the sensors do not detect the temperatures of the inner and outer races of the bearing.

However, the stator cannot be sufficiently cooled by this configuration, and the heated lubricating liquid acts as a thermal medium heating the housing.

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